Secondary Oxidation of Steel
Secondary oxidation is a common phenomenon in the processing of steel. It refers to the oxidation process in which steel is corroded and reacts with oxygen in the air after being heated to an elevated temperature. At present, the secondary oxidation of steel mainly occurs in the following flows:
1. furnace forging temperature
Secondary oxidation of steel mainly occurs at high temperature during the forging process. That is, the oxidation reaction process of steel is the main route when the steel is heated to a certain temperature, and the oxide film of iron and iron oxide is generated on the surface of the steel parts. This oxide film will reduce the strength and plasticity of the steel parts, and even cause defects in the processing of steel parts.
2. Brazing heat-resistant temperature
When soldering parts at high temperature, the oxidation of steel will occur due to the direct contact with high temperature flame. The generated oxide film will also reduce the bonding strength of steel and solder.
3. Heat treatment temperature
In the heat treatment process of steel, such as annealing, quenching and tempering, the steel material will be heated to a certain temperature, and the oxidation reaction of the steel material will start. The macroscopic oxidation of steel will be caused by the generation of oxide film, resulting in continuous reduction of mechanical properties of steel, and even cracks in severe cases.
To prevent secondary oxidation of steel in production, the following measures should be taken in application.
1. Reduce the heating temperature
The secondary oxidation of steel is closely related to the temperature. Reducing the heating temperature can reduce the incidence of secondary oxidation of steel. Generally, its best to keep the temperature of steel below 450℃ when forging or heat-treating, so as to reduce the chance of oxidation.
2. Use protective medium
That is to inlay a layer of protective medium between the heated material and the flame, so as to separate the material from direct contact with the flame, thereby reducing the chance of being oxidized by the flame. Common protective media include oil slag, copper slag, heavy wall borosilicate glass beads, fused quartz sand and so on.
3. Choose high-quality wear-resistant steel
Using high quality wear resistant steel can reduce the possibility of wear and tear and oxidation of steel during forging and heat treatment. It is best to choose materials with higher strength and better oxidation resistance.
4. Develop a nitrogen protection furnace
This method can completely separate the heated steel from contact with any oxygen source, so as to obtain a more perfect protection effect. The nitrogen protection furnace can protect the heated steel parts from the oxidation reaction of oxygen in the air, and ensure that the steel parts are free from oxidation and wear.
In short, the rolling and forging of steel parts will form oxidation reaction due to high temperature, which will reduce the mechanical properties of steel and cause serious wear. Therefore, in order to reduce the occurrence of secondary oxidation of steel, enterprises should use high quality wear-resistant steel parts, develop a nitrogen protection furnace, reduce the heating temperature and choose a suitable protective medium, so as to further reduce the chance of steel oxidation.
